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Babatunde Aina - One of the best experts on this subject based on the ideXlab platform.

  • Steady fully developed mixed convection flow in a vertical micro-Concentric-Annulus with heat generating/absorbing fluid: An exact solution
    Elsevier, 2018
    Co-Authors: Basant K. Jha, Michael O. Oni, Babatunde Aina
    Abstract:

    This study investigates the influence of heat generating/absorbing fluid on fully developed mixed convection flow in a vertical micro-Concentric-Annulus (MCA) taking into account the velocity slip and temperature jump at the outer surface of inner cylinder and inner surface of outer cylinder. Exact solution of momentum and energy equations is derived separately in terms of Bessel’s function of first and second kind for heat generating fluid and modified Bessel’s function of first and second kind for heat absorbing fluid. The solutions obtained are graphically represented and the effects of governing parameters on flow formation and heat transfer aspects are investigated in detail. During the course of numerical computations, it is found that increase in heat generation parameter enhanced the temperature and velocity of the fluid but reduced the rate of heat transfer at the outer surface of the inner cylinder while the reverse trend is observed for heat absorbing fluid. Keywords: Mixed convection, Micro-Concentric-Annulus (MCA), Velocity slip, Temperature jump, Heat generating/absorbing flui

  • Steady fully developed mixed convection flow in a vertical micro-Concentric-Annulus with heat generating/absorbing fluid: An exact solution
    Ain Shams Engineering Journal, 2018
    Co-Authors: Basant K. Jha, Michael O. Oni, Babatunde Aina
    Abstract:

    Abstract This study investigates the influence of heat generating/absorbing fluid on fully developed mixed convection flow in a vertical micro-Concentric-Annulus (MCA) taking into account the velocity slip and temperature jump at the outer surface of inner cylinder and inner surface of outer cylinder. Exact solution of momentum and energy equations is derived separately in terms of Bessel’s function of first and second kind for heat generating fluid and modified Bessel’s function of first and second kind for heat absorbing fluid. The solutions obtained are graphically represented and the effects of governing parameters on flow formation and heat transfer aspects are investigated in detail. During the course of numerical computations, it is found that increase in heat generation parameter enhanced the temperature and velocity of the fluid but reduced the rate of heat transfer at the outer surface of the inner cylinder while the reverse trend is observed for heat absorbing fluid.

  • steady fully developed mixed convection flow in a vertical micro Concentric Annulus with heat generating absorbing fluid an exact solution
    Ain Shams Engineering Journal, 2016
    Co-Authors: Basant K. Jha, Michael O. Oni, Babatunde Aina
    Abstract:

    Abstract This study investigates the influence of heat generating/absorbing fluid on fully developed mixed convection flow in a vertical micro-Concentric-Annulus (MCA) taking into account the velocity slip and temperature jump at the outer surface of inner cylinder and inner surface of outer cylinder. Exact solution of momentum and energy equations is derived separately in terms of Bessel’s function of first and second kind for heat generating fluid and modified Bessel’s function of first and second kind for heat absorbing fluid. The solutions obtained are graphically represented and the effects of governing parameters on flow formation and heat transfer aspects are investigated in detail. During the course of numerical computations, it is found that increase in heat generation parameter enhanced the temperature and velocity of the fluid but reduced the rate of heat transfer at the outer surface of the inner cylinder while the reverse trend is observed for heat absorbing fluid.

Basant K. Jha - One of the best experts on this subject based on the ideXlab platform.

  • Steady fully developed mixed convection flow in a vertical micro-Concentric-Annulus with heat generating/absorbing fluid: An exact solution
    Elsevier, 2018
    Co-Authors: Basant K. Jha, Michael O. Oni, Babatunde Aina
    Abstract:

    This study investigates the influence of heat generating/absorbing fluid on fully developed mixed convection flow in a vertical micro-Concentric-Annulus (MCA) taking into account the velocity slip and temperature jump at the outer surface of inner cylinder and inner surface of outer cylinder. Exact solution of momentum and energy equations is derived separately in terms of Bessel’s function of first and second kind for heat generating fluid and modified Bessel’s function of first and second kind for heat absorbing fluid. The solutions obtained are graphically represented and the effects of governing parameters on flow formation and heat transfer aspects are investigated in detail. During the course of numerical computations, it is found that increase in heat generation parameter enhanced the temperature and velocity of the fluid but reduced the rate of heat transfer at the outer surface of the inner cylinder while the reverse trend is observed for heat absorbing fluid. Keywords: Mixed convection, Micro-Concentric-Annulus (MCA), Velocity slip, Temperature jump, Heat generating/absorbing flui

  • Steady fully developed mixed convection flow in a vertical micro-Concentric-Annulus with heat generating/absorbing fluid: An exact solution
    Ain Shams Engineering Journal, 2018
    Co-Authors: Basant K. Jha, Michael O. Oni, Babatunde Aina
    Abstract:

    Abstract This study investigates the influence of heat generating/absorbing fluid on fully developed mixed convection flow in a vertical micro-Concentric-Annulus (MCA) taking into account the velocity slip and temperature jump at the outer surface of inner cylinder and inner surface of outer cylinder. Exact solution of momentum and energy equations is derived separately in terms of Bessel’s function of first and second kind for heat generating fluid and modified Bessel’s function of first and second kind for heat absorbing fluid. The solutions obtained are graphically represented and the effects of governing parameters on flow formation and heat transfer aspects are investigated in detail. During the course of numerical computations, it is found that increase in heat generation parameter enhanced the temperature and velocity of the fluid but reduced the rate of heat transfer at the outer surface of the inner cylinder while the reverse trend is observed for heat absorbing fluid.

  • MHD Transient Free Convection Flow in Vertical Concentric Annulus with Isothermal and Adiabatic Boundaries
    International Journal of Engineering and Technologies, 2017
    Co-Authors: Basant K. Jha, Taiwo S. Yusuf
    Abstract:

    This paper presents MHD transient flow in an infinite vertical Concentric Annulus when the fluid is set in motion by free convection current occurring in the Annulus as a result of application of isothermal heating on the inner surface of the outer cylinder while the outer surface of the inner cylinder is thermally insulated. The solution of the governing equations are obtained using the well-known Laplace transform technique while the Riemann-sum approximation method has been used to invert the solution from Laplace domain to time domain. The numerical values obtained using Riemann-sum approximation approach is validated by presenting a comparison with the values obtained using the implicit finite difference method as well as the steady-state solution. These comparisons with the steady state solution shows a remarkable agreement at large value of time. The effect of the governing parameters on the velocity field, temperature field, mass flow rate as well as the skin-friction on both surfaces of the Annulus have been analysed and presented with the aid of line graph. Generally, we observed that the mass flow rate and skin friction at the isothermally heated surface increases with increase in radius ratio. However, the reverse is seen at the thermally insulated surface as the skin-friction decreases with increase in radius ratio.

  • steady fully developed mixed convection flow in a vertical micro Concentric Annulus with heat generating absorbing fluid an exact solution
    Ain Shams Engineering Journal, 2016
    Co-Authors: Basant K. Jha, Michael O. Oni, Babatunde Aina
    Abstract:

    Abstract This study investigates the influence of heat generating/absorbing fluid on fully developed mixed convection flow in a vertical micro-Concentric-Annulus (MCA) taking into account the velocity slip and temperature jump at the outer surface of inner cylinder and inner surface of outer cylinder. Exact solution of momentum and energy equations is derived separately in terms of Bessel’s function of first and second kind for heat generating fluid and modified Bessel’s function of first and second kind for heat absorbing fluid. The solutions obtained are graphically represented and the effects of governing parameters on flow formation and heat transfer aspects are investigated in detail. During the course of numerical computations, it is found that increase in heat generation parameter enhanced the temperature and velocity of the fluid but reduced the rate of heat transfer at the outer surface of the inner cylinder while the reverse trend is observed for heat absorbing fluid.

Amin Shahsavar - One of the best experts on this subject based on the ideXlab platform.

  • Free convection heat transfer and entropy generation analysis of water-Fe3O4/CNT hybrid nanofluid in a Concentric Annulus
    International Journal of Numerical Methods for Heat & Fluid Flow, 2019
    Co-Authors: Amin Shahsavar, Pouyan Talebizadeh Sardari, Davood Toghraie
    Abstract:

    This paper aims to numerically investigate the heat transfer and entropy generation characteristics of water-based hybrid nanofluid in natural convection flow inside a Concentric horizontal Annulus.,The hybrid nanofluid is prepared by suspending tetramethylammonium hydroxide-coated Fe3O4 (magnetite) nanoparticles and gum arabic (GA)-coated carbon nanotubes (CNTs) in water. The effects of nanoparticle volume concentration and Rayleigh number on the streamlines, isotherms, average Nusselt number and the thermal, frictional and total entropy generation rates are investigated comprehensively.,Results show the advantageous effect of hybrid nanofluid on the average Nusselt number. Furthermore, the study of entropy generation shows the increment of both frictional and thermal entropy generation rates by increasing Fe3O4 and CNT concentrations at various Rayleigh numbers. Increasing Rayleigh number from 103 to 105, at Fe3O4 concentration of 0.9 per cent and CNT concentration of 1.35 per cent, increases the average Nusselt number, thermal entropy generation rate and frictional entropy generation rate by 224.95, 224.65 and 155.25 per cent, respectively. Moreover, increasing the Fe3O4 concentration from 0.5 to 0.9 per cent, at Rayleigh number of 105 and CNT concentration of 1.35 per cent, intensifies the average Nusselt number, thermal entropy generation rate and frictional entropy generation rate by 18.36, 22.78 and 72.7 per cent, respectively.,To the best knowledge of the authors, there are not any archival publications considering the detailed behaviour of the natural convective heat transfer and entropy generation of hybrid nanofluid in a Concentric Annulus.

  • free convection heat transfer and entropy generation analysis of water fe3o4 cnt hybrid nanofluid in a Concentric Annulus
    International Journal of Numerical Methods for Heat & Fluid Flow, 2019
    Co-Authors: Amin Shahsavar, Pouyan Talebizadeh Sardari, Davood Toghraie
    Abstract:

    This paper aims to numerically investigate the heat transfer and entropy generation characteristics of water-based hybrid nanofluid in natural convection flow inside a Concentric horizontal Annulus.,The hybrid nanofluid is prepared by suspending tetramethylammonium hydroxide-coated Fe3O4 (magnetite) nanoparticles and gum arabic (GA)-coated carbon nanotubes (CNTs) in water. The effects of nanoparticle volume concentration and Rayleigh number on the streamlines, isotherms, average Nusselt number and the thermal, frictional and total entropy generation rates are investigated comprehensively.,Results show the advantageous effect of hybrid nanofluid on the average Nusselt number. Furthermore, the study of entropy generation shows the increment of both frictional and thermal entropy generation rates by increasing Fe3O4 and CNT concentrations at various Rayleigh numbers. Increasing Rayleigh number from 103 to 105, at Fe3O4 concentration of 0.9 per cent and CNT concentration of 1.35 per cent, increases the average Nusselt number, thermal entropy generation rate and frictional entropy generation rate by 224.95, 224.65 and 155.25 per cent, respectively. Moreover, increasing the Fe3O4 concentration from 0.5 to 0.9 per cent, at Rayleigh number of 105 and CNT concentration of 1.35 per cent, intensifies the average Nusselt number, thermal entropy generation rate and frictional entropy generation rate by 18.36, 22.78 and 72.7 per cent, respectively.,To the best knowledge of the authors, there are not any archival publications considering the detailed behaviour of the natural convective heat transfer and entropy generation of hybrid nanofluid in a Concentric Annulus.

  • heat transfer and entropy generation optimization for flow of a non newtonian hybrid nanofluid containing coated cnt fe3o4 nanoparticles in a Concentric Annulus
    Journal of The Taiwan Institute of Chemical Engineers, 2018
    Co-Authors: Amin Shahsavar, Mehdi Moradi, Mehdi Bahiraei
    Abstract:

    Abstract This research attempts to investigate the effects of concentration and radius ratio on convective heat transfer and entropy generation of a non-Newtonian hybrid nanofluid flowing through a Concentric Annulus. The nanofluid is prepared by suspending tetramethylammonium hydroxide (TMAH) coated Fe3O4 (magnetite) nanoparticles and gum arabic (GA) coated carbon nanotubes (CNTs) in water. Variable thermal conductivity and viscosity are used in simulations. The convective heat transfer coefficient of inner and outer walls, and total entropy generation augment with increasing Fe3O4 and CNT concentrations. Increasing radius ratio from 0.2 to 0.8, at CNT concentration of 1.1% and Fe3O4 concentration of 0.7%, decreases the heat transfer coefficient of inner wall by 85.05%, while increases that of outer wall by 35.49%. Models of convective heat transfer coefficient of both walls and total entropy generation are developed using neural network. Genetic algorithm is used with compromise programming to achieve optimal cases with maximum heat transfer and minimum entropy generation. In this method, the objective functions are mixed and the problem transforms into a single-objective optimization. Finally, applying the nanofluid with high concentrations is recommended for all conditions except the cases in which importance of entropy generation is considered much greater than that of heat transfer.

  • Heat transfer and entropy generation optimization for flow of a non-Newtonian hybrid nanofluid containing coated CNT/Fe3O4 nanoparticles in a Concentric Annulus
    Journal of the Taiwan Institute of Chemical Engineers, 2018
    Co-Authors: Amin Shahsavar, Mehdi Moradi, Mehdi Bahiraei
    Abstract:

    Abstract This research attempts to investigate the effects of concentration and radius ratio on convective heat transfer and entropy generation of a non-Newtonian hybrid nanofluid flowing through a Concentric Annulus. The nanofluid is prepared by suspending tetramethylammonium hydroxide (TMAH) coated Fe3O4 (magnetite) nanoparticles and gum arabic (GA) coated carbon nanotubes (CNTs) in water. Variable thermal conductivity and viscosity are used in simulations. The convective heat transfer coefficient of inner and outer walls, and total entropy generation augment with increasing Fe3O4 and CNT concentrations. Increasing radius ratio from 0.2 to 0.8, at CNT concentration of 1.1% and Fe3O4 concentration of 0.7%, decreases the heat transfer coefficient of inner wall by 85.05%, while increases that of outer wall by 35.49%. Models of convective heat transfer coefficient of both walls and total entropy generation are developed using neural network. Genetic algorithm is used with compromise programming to achieve optimal cases with maximum heat transfer and minimum entropy generation. In this method, the objective functions are mixed and the problem transforms into a single-objective optimization. Finally, applying the nanofluid with high concentrations is recommended for all conditions except the cases in which importance of entropy generation is considered much greater than that of heat transfer.

Godwin A. Chukwu - One of the best experts on this subject based on the ideXlab platform.

  • Unsteady axial laminar Couette flow of power-law fluids in a Concentric Annulus
    Industrial & Engineering Chemistry Research, 1996
    Co-Authors: Yuan Wang, Godwin A. Chukwu
    Abstract:

    The unsteady laminar couette flow of non-Newtonian power-law fluids in a Concentric Annulus is a flow phenomenon that can be applied to predict the surge or swab pressure encountered when running or pulling pipes in a liquid-filled borehole. It is similar to a moving cylinder, Concentrically placed in a liquid-filled outer cylinder. This flow phenomenon has a wide variety of applications in the solution of problems in petroleum, chemical, mechanical, and ceramic industries. Several numerical models have been proposed by several authors for surge or swab pressure predictions. Though previous investigators had reported that the magnitude of the surge or swab pressure is determined by the annular geometry, the moving pipe velocity, and the drilling fluid properties, there has been no reported simple analytical presentation of the application of the unsteady couette flow phenomenon to predict either the surge or swab pressure which occurs when the casing pipes are in motion in a liquid-filled borehole. In thi...

Hyung Jin Sung - One of the best experts on this subject based on the ideXlab platform.

  • Characterization of the three-dimensional turbulent boundary layer in a Concentric Annulus with a rotating inner cylinder
    Physics of Fluids, 2006
    Co-Authors: Seo Yoon Jung, Hyung Jin Sung
    Abstract:

    Direct numerical simulations of fluid flow through a Concentric Annulus with a rotating inner wall were performed at ReDh=8900. To elucidate the modifications of the near-wall turbulent structure induced by rotation of the inner wall, we compared data obtained at rotation rates of N=0.0 and 0.429 for a system with a radius ratio (R*) of 0.5. Conditional quadrant/octant analysis and probability density functions of the velocity fluctuations revealed distinctive features of the three-dimensional turbulent boundary layer (3DTBL) in the Concentric Annulus with a rotating inner wall. Coherent structures near the inner wall were identified by a λ2-based eduction scheme to give the detailed information on the activated near-wall turbulent structures. The ensemble-averaging of the educed coherent vortices showed that enhanced ejections near the vortices were primarily responsible for the augmented turbulent structures. The alteration of the turbulent structures was attributed to the centrifugal force arising from rotation of the inner wall. The assumption of Littell and Eaton on the cause of the altered turbulent structures in 3DTBLs was invalid in the present study. Taken together, the present results showed that the 3DTBL in a rotating Concentric Annulus has features different from those observed in other types of 3DTBL due to the transverse curvature.Direct numerical simulations of fluid flow through a Concentric Annulus with a rotating inner wall were performed at ReDh=8900. To elucidate the modifications of the near-wall turbulent structure induced by rotation of the inner wall, we compared data obtained at rotation rates of N=0.0 and 0.429 for a system with a radius ratio (R*) of 0.5. Conditional quadrant/octant analysis and probability density functions of the velocity fluctuations revealed distinctive features of the three-dimensional turbulent boundary layer (3DTBL) in the Concentric Annulus with a rotating inner wall. Coherent structures near the inner wall were identified by a λ2-based eduction scheme to give the detailed information on the activated near-wall turbulent structures. The ensemble-averaging of the educed coherent vortices showed that enhanced ejections near the vortices were primarily responsible for the augmented turbulent structures. The alteration of the turbulent structures was attributed to the centrifugal force arising from...

  • Large-eddy simulation of turbulent flow in a Concentric Annulus with rotation of an inner cylinder
    International Journal of Heat and Fluid Flow, 2005
    Co-Authors: Seo Yoon Chung, Hyung Jin Sung
    Abstract:

    Large-eddy simulations of the turbulent flow in a Concentric Annulus with inner wall rotation were performed at ReDh = 8900 for three rotation rates (N = 0.2145, 0.429 and 0.858). The main emphasis of this work was on the destabilization of the near-wall turbulent structures due to rotation of the inner wall. The turbulent structures close to the inner wall were scrutinized by computing the lower-order statistics. The anisotropy invariant map for the Reynolds stress tensor and the invariant function revealed that rotation of the inner wall altered the anisotropy of the turbulent structure. The probability density functions of the velocity fluctuations and the splat/anti-splat process were examined to create a more complete picture of the contributions of the flow events to turbulent production. The present numerical results indicate that the alteration of the turbulent structures can be attributed to the destabilizing effect of rotation of the inner wall, which gives rise to an augmentation of sweep and ejection events. 2004 Elsevier Inc. All rights reserved.